[lld][WebAssembly] Fix stub library parsing with windows line endings

Also, fix checking of first line in ::parse.  We can't use the
::getLines helper here since that already does comment stripping
internally.

Differential Revision: https://reviews.llvm.org/D147548

(cherry picked from commit d9d840c)

lld/test/wasm/Inputs/.gitattributes

@@ -0,0 +1,3 @@
+# ensures that we test parsing of stub libraries that contain
+# windows line endings
+libstub.so text eol=crlf

lld/wasm/Driver.cpp

@@ -281,7 +281,7 @@ void LinkerDriver::addFile(StringRef path) {
     files.push_back(createObjectFile(mbref));
     break;
   case file_magic::unknown:
-    if (mbref.getBuffer().starts_with("#STUB\n")) {
+    if (mbref.getBuffer().starts_with("#STUB")) {
       files.push_back(make<StubFile>(mbref));
       break;
     }

lld/wasm/InputFiles.cpp

@@ -691,12 +691,16 @@ StringRef strip(StringRef s) {
 }
 
 void StubFile::parse() {
-  bool first = false;
+  bool first = true;
+
+  SmallVector<StringRef> lines;
+  mb.getBuffer().split(lines, '\n');
+  for (StringRef line : lines) {
+    line = line.trim();
 
-  for (StringRef line : args::getLines(mb)) {
     // File must begin with #STUB
     if (first) {
-      assert(line == "#STUB\n");
+      assert(line == "#STUB");
       first = false;
     }
 
@@ -713,10 +717,10 @@ void StubFile::parse() {
     symbolDependencies[sym] = {};
 
     while (rest.size()) {
-      StringRef first;
-      std::tie(first, rest) = rest.split(',');
-      first = strip(first);
-      symbolDependencies[sym].push_back(first);
+      StringRef dep;
+      std::tie(dep, rest) = rest.split(',');
+      dep = strip(dep);
+      symbolDependencies[sym].push_back(dep);
     }
   }
 }